1. Field of the Invention
The present invention relates to telephone wiring interconnect apparatus and method, and more particularly, to an interconnect apparatus of the type commonly used in a network interface device (NID), such as a protected terminal device (PID) or line module. The apparatus is used to interconnect wiring from a telephone service provider with subscriber wiring. Specifically, the present invention relates to an improved telephone interconnect apparatus that can withstand overcurrent and overvoltage conditions.
2. Description of the Related Art
Telephone service is provided by a telephone company (xe2x80x9cTelcoxe2x80x9d) to a number of different subscribers. Each subscriber may purchase as many separate telephone lines as desired and equip his or her home or business with various telephone equipment. Subscribers are responsible for proper operation of the telephone equipment and the Telco is responsible for proper operation of the telephone network up to the interface between the Telco wiring and the subscriber wiring. Therefore, it is desirable to provide a telephone network interface device (NID) to serve as demarcation point between the Telco wiring and the subscriber wiring. FIG. 1 illustrates a typical prior art NID 10. The NID 10 may be mounted to an exterior wall of a house or commercial building 2. The Telco wiring 4 enters the NID and terminates in a locked inner enclosure 12, which is shown in the open position for purposes of clarity. The Telco wiring 4 may come in bundle, of, for example, twisted pair wires. The bundle of twisted pair wires can-be split and each pair terminated into a connector block within the inner enclosure 12.
The inner enclosure 12 is preferably locked to prevent unauthorized access by the subscriber or vandals. Typically, each subscriber telephone line is serviced by one set of twisted pair wires, commonly referred to as the xe2x80x9ctipxe2x80x9d and xe2x80x9cringxe2x80x9d wires. Each of the twisted pair wires is electrically connected to an interconnect apparatus, such as a protected terminal device (PTD) or line module 100, located adjacent the inner enclosure 12. In other words, the tip and ring wires from one twisted pair are inserted into one end of the interconnect apparatus 100 and electrically coupled to a pair of conductors within the apparatus. The interconnect apparatus 100 is typically a modular device that can be mounted in the NID and easily replaced if rendered inoperable.
Referring to FIGS. 2A to 2E, a prior art line module 100 is shown in greater detail. The line module 100 has a housing 102 and a cover 104 that can pivot between a closed position, as shown in FIG. 2A, and an open position, as shown in FIG. 2B. The housing 102 of the line module 100 has a pair of insertion channels 124 that allow that Telco wires 4 to be electrically coupled with a pair of contacts 122 (FIG. 2E) located in an integrated jack 112. As shown, the jack 122 is a conventional RJ-11 jack. The cover 104 may be connected to the line module 100 by a hinge 120 (FIG. 2C) so that the cover 104 can be rotated away from the housing 102 of the line module 100 to permit access to the jack 112. As mentioned, the jack 112 has a pair of contacts 122 that are electrically coupled to the tip and ring wires. Likewise, plug 110 attached to the cover 104 has a complementary pair of conductors 114 that make contact with the jack contacts 122 when the plug 110 is engaged in the jack 112. The subscriber wires 6 are connected to a pair of terminals 118 provided on a portion of the line module 100 known as the bridge 108. The plug conductors 114 are also electrically coupled to the terminals 118. Thus, when the cover 104 is closed, an electrical circuit is completed between the Telco wires 4 and the subscriber wires 6. When the cover 104 is opened, the subscriber wires 6 are disconnected from the Telco wires 4. However, a test plug (not shown) can be plugged into the jack 112 to determine if the Telco wires 4 up to the line module 100 are conducting properly. As shown in FIGS. 2C and 2D, the bridge 108 is removable, and thus, replaceable if rendered inoperable. However, line module 100 may also be provided with a non-removable bridge.
The spacing and size of the plug conductors 114 and the jack conductors 122 are sources of failure when the line module 100 is subjected to overvoltage and overcurrent conditions. For example, a lightning strike on a telephone line may cause a voltage spike that will result in an electric arc between the tip and ring contacts of either the jack or the plug. In other words, the tip and ring wires are at different voltages. An overvoltage event magnifies the difference and may cause an electrical arc to jump between the closely spaced contacts. The contacts in RJ-11 plugs and sockets are relatively small gauge, typically 24 AWG or 25 AWG. An overcurrent event may result in the plug and jack conductors in contact with each other welding together. In either event, the line module 100 is rendered inoperable.
U.S. Pat. No. 5,153,910 discloses an example of a protected terminal device (PTD) for a NID used to connect Telco wiring with subscriber wiring. When the cover of the PTD is closed, an actuator presses a set of conductors into contact with a complementary set of thin lead contacts. The lead contacts in turn are connected to the Telco wiring. The subscriber wiring is connected through two terminal screws to the set of conductors. Thus, an electrical signal path is created from the subscriber wiring, through the terminal screws and conductors, and into lead contacts. While this simple design allows for easy connection of the subscriber and Telco wiring, it does not address the causes of the arcing or welding failure modes. Specifically, arcing may occur between the lead contacts because they are closely spaced. Furthermore, the small gauge lead contacts may become welded to the conductors.
It is thus apparent a particular need exists for an improved interconnect apparatus that can withstand overcurrent conditions and overvoltage conditions.
It is further apparent that a particular need exists for an improved interconnect apparatus including a test plug that remains functional when a cover is removed from the bridge and the electrical circuit between the Telco wires and the subscriber wires is broken.
It is further apparent that a particular need exists for an improved interconnect apparatus that can withstand overvoltage and overcurrent conditions regardless of whether the bridge is fixed or removable.
The present invention relates to an improved interconnect apparatus, such as a protected terminal device (PTD) or line module, that can withstand overcurrent and overvoltage event, such as a lightening strike. The interconnect apparatus may, for example, be mounted within a conventional network interface device (NID). The interconnect apparatus uses large gauge by-pass conductors for signal transmission from the Telco to the subscriber rather than small gauge contacts. However, the jack located in the housing of the interconnect apparatus retains standard sized contacts that will interface with conventional test plugs.
In one embodiment, the improved interconnect apparatus includes a housing having a removable bridge and cover assembly. The bridge includes terminals for connection to the subscriber wires. The housing includes a jack having a first set of by-pass conductors and a first set of contacts. The first set of by-pass conductors include one conductor for the tip wire and one conductor for the ring wire. The first set of by-pass conductors oppose a second set of by-pass conductors located on a plug. The plug can be attached to the cover. When the plug is engaged with the jack, the first set of by-pass conductors electrically couple with the second set of by-pass conductors to complete an electrical circuit between the Telco wires and the subscriber wires. The plug, however, does not require a second set of contacts to complete an electrical circuit with the first set of contacts. When the cover is opened, the first and second set of by-pass conductors are uncoupled and the electrical circuit therebetween is broken. In the event of an overcurrent condition, the first and second sets of by-pass conductors can withstand the current surge because of their increased dimensions. In the event of an overvoltage condition, arcing is largely inhibited by the spacing (i.e., separation) between the by-pass conductors on the plug and jack, and a non-conductive grease between the first set of contacts. Further, the plug may have a ridge that fits between, and thus, isolates the contacts on the jack.
In another embodiment, the improved interconnect apparatus has a cover pivotally hinged on the housing to permit access to a jack. The cover is provided with a dummy plug or actuator. The dummy plug does not have either a second set of by-pass conductors or a second set of contacts. Instead the housing of the interconnect apparatus contains both a first set of by-pass conductors and a second set of by-pass conductors. The first and second sets of by-pass conductors are mounted within the housing substantially parallel, but apart from one another. Further, one or both sets of conductors can be cantilevered to provide an elastic spring force when one set is moved in the direction of the other. The first set of by-pass conductors is electrically coupled to a first set of contacts exposed in the jack. The first set of by-pass conductors is further connected to the Telco wires, while the second set of by-pass conductors is connected to the subscriber wires. When the dummy plug is inserted into the jack, the tip of the plug forces one set of the by-pass conductors into contact with the other set of by-pass conductors. An electrical circuit is thereby completed between the Telco wires and the subscriber wires. However, when the cover is opened and the plug is removed, the sets of by-pass conductors move apart due to the elastic spring force and the electrical circuit is broken. Furthermore, the first set of conductors in the jack is exposed and a conventional test plug can be inserted. The jack, however, is dimensioned to prevent the tip of the test plug from creating contact between the first and second sets of by-pass conductors. Arcing is largely inhibited by providing a non-conductive grease between the first set of contacts.
The present invention relates broadly to telephone wiring interconnect apparatus and methods. As such, the invention relates to more than the improved interconnect apparatus and the specific wiring configuration disclosed and shown herein. In particular, a method of connecting Telco wires to subscribe wires through the improved interconnect apparatus is also disclosed.